1. Field of the Invention
The present invention relates to a mobile radio system equipped with means for suppressing an output of interference radio waves in the technical field of mobile radio.
2. Description of the Related Art
FIG. 3 is a schematic diagram showing the structure of a conventional mobile radio transmitter. In FIG. 3, reference numeral 1 represents data to be transmitted, reference numeral 2 represents a transmitter unit, and reference numeral 3 represents an antenna. Data 1 is supplied to the transmitter unit 2 and is modulated and transmitted as a radio wave output 4 from the antenna 3. Reference numeral 5 represents a control CPU which supplies a transmission output control signal 16 to the transmitter unit 2. The transmission output control signal controls the on/off state of transmission, transmission power level, and the like.
The method of controlling a radio wave output of the mobile radio apparatus constructed as indicated above will now be described. Referring to FIG. 3, if there is data 1 to be transmitted, the control CPU 5 controls the transmission on/off state, transmission power level, and the like of a transmission power amplifier and the like in the transmitter unit 2. The data modulated at the transmitter unit 2 is transmitted as the radio wave output 4 from the antenna 1 at a predetermined transmission power level.
In the above-described manner, the control CPU controls the radio wave output of the conventional mobile radio apparatus described above.
With such a conventional mobile radio apparatus, however, if the control CPU controlling the transmission power of the mobile radio apparatus crashes or the hardware of the mobile radio apparatus breaks down, there is a possibility of transmitting radio waves at an unexpected timing or at an unexpected power level. For example, in a mobile radio system using CDMA (code division multiple access), users in one area are assigned the same carrier. Therefore, the radio wave output of one mobile radio apparatus may become an interference to an other mobile radio apparatus. It is therefore necessary for each mobile radio apparatus to control its transmission power correctly. If a mobile radio apparatus transmits its radio wave output at a power level larger than the predetermined level, another mobile radio apparatus may possibly be interfered with by the high power radio wave output. In such a case, the number of users in one area must be reduced. The mobile radio system may become unable to operate if a mobile radio apparatus become defective and transmits too large a radio wave output.
The above-described problems are also associated with parent-child communication system (JP-A-3-240328) in which any abnormality between a parent apparatus and a child apparatus is monitored.
The present invention solves the above-described problems of the prior art and aims at providing an excellent mobile radio system capable of stopping or suppressing a radio wave output when an abnormality of a mobile radio apparatus is detected.
In order to achieve the above object, the mobile radio apparatus of a mobile radio system of the invention includes a CPU for controlling the mobile radio apparatus and monitoring the status of the hardware of the mobile radio apparatus, a transmitter unit for transmitting data in the form of radio waves, and a CPU monitor unit, wherein the CPU regularly monitors and checks for any abnormalities in the hardware of the mobile radio apparatus, the CPU monitor unit regularly monitors and checks for any abnormalities in the CPU, and if one of the CPU and CPU monitor unit detects an abnormality, a signal for inhibiting or suppressing the radio wave output is supplied to the transmitter unit.
Furthermore, a base station of the mobile radio system of the invention includes means for transmitting a signal for inhibiting or suppressing the radio wave output to a mobile radio apparatus when the base station detects that the mobile radio apparatus is abnormal.
According to the present invention, the CPU controlling a mobile radio apparatus regularly monitors and checks for abnormalities in the hardware of the mobile radio apparatus, and the CPU monitor unit regularly monitors and checks for abnormalities in the CPU. Therefore, if one of the hardware of the mobile radio apparatus and the CPU becomes abnormal, the radio wave output of the transmitter unit is inhibited or suppressed so that interference to the system can be avoided.
Furthermore, according to the present invention, if the base station detects an abnormality in a mobile radio apparatus, it transmits a signal like the signal supplied from the CPU or CPU monitor unit to the transmitter unit of the mobile radio apparatus, to the mobile radio apparatus. It is therefore possible to inhibit or suppress the output of radio waves from the transmitter unit of the mobile radio apparatus, thereby avoiding interference to the system.